On the Linux client, screen resolution scaling can make a difference to how fonts appear in the Admin By Request GUI. If the font appears distorted, large, compressed or with overlapping lines (or is simply unreadable), check the UI scaling percentage (Settings > Displays > Scale). If the value is greater than 100%, fonts in the GUI panels can appear distorted:

This will be fixed in a future release of the Linux client. Until then, the workaround is to reduce scaling to 100%. Note that functionality is unchanged - the client will still work as intended.